The proliferation of portable media devices such as MP3 music players, digital cameras, media-enabled cellular telephone and others has encouraged the exchange of media objects of many types. For example, a user who wishes to view the contents of a digital camera may attach that device to their computer or other client, to view the collection of photographs stored on the memory card of that device, for instance to choose selected pictures to upload, print or delete. Music files are another commonly exchanged media object.
As illustrated in FIG. 1, when a user operating a client or initiator sends a request to the portable media device to see a list of all stored media objects, the device's built-in intelligence may mediate that request to access the internal content list. Many or most media players store content in object format, in which the media object such as a sound file or digital photograph stored in binary format is paired with a set of properties or attributes describing that object. For example the properties may include a codec type for sound files, a color depth for digital photographs, or other attributes or characteristics. It may be necessary for the device reading those objects to have access to the properties as well as the underlying object, to play or consume them.
When the user is asking for a list or enumeration of those objects, the media device may according to known protocol technologies respond with a content list or ID list which identifies the set of songs, photographs, video clips or other objects or media stored on the device, in total. However, according to known transfer protocols that type of responsive data does not include the set of properties paired with each object (nor the objects themselves). Among other things, this means that the initiator can not determine attributes for the media inventory which it has just received, so that for example the play time, artist, language or other properties of a set of songs can not be viewed just by retrieving the content list. Rather, the portable media device must sequentially request the set of properties paired with each object identified in the content list which has been retrieved, one after the other. In another regard, this may mean that all media objects on the portable device must be parsed to locate a single song, photograph or other content of interest.
However, the storage subsystems of such portable media machines may often be optimized for the device's own internal access purposes, and not for external delivery. Moreover, because the access time for the storage embedded in the media device, for example a CD-ROM drive, microdrive or other rotating or electronic media, as well as internal processing throughput is typically significantly slower than the access or processing time of the initiating client, the need to separately request the properties for each object can create a substantial access bottleneck.
On for example a portable music device storing hundreds or thousands or MP3 or other audio files, this may amount to delays of many minutes or more as the initiator is forced to transmit hundreds or thousands of object property requests to the device, even when those requests and the response are transmitted over relatively fast connections such as USB 2.0 or Firewire™ connections. Other problems in media object management and portability exist.